Expansion seal

ABSTRACT

A sealing system for a gas turbine engine includes a first surface and a second surface spaced a dimension away from the first surface defining a gap through which a fluid can flow. At least one recess is formed in one of the first surface and the second surface and is oriented such that the fluid flow through the gap crosses the at least one recess. The recess is configured to restrict the fluid flow through the gap in comparison to if the at least one recess were not present, all other things being equal.

BACKGROUND

This disclosure relates to a gas turbine engine, and more particularlyto gaspath leakage seals for gas turbine engines.

Gas turbine engines, such as those used to power modern commercial andmilitary aircrafts, generally include a compressor section to pressurizean airflow, a combustor section for burning hydrocarbon fuel in thepresence of the pressurized air, and a turbine section to extract energyfrom the resultant combustion gases. The airflow flows along a gas paththrough the gas turbine engine. Along the gas path, there are manypotential leakage paths, such as joints between mating components, thatcan reduce the efficiency of the system.

Traditionally, the leakage paths are addressed by the inclusion ofphysical seals, such as rope seals or W seals between the mating parts.Such methods, however, suffer challenges due to durability, FOD (foreignobject damage), sealing effectiveness, cost, and design space/sizerestrictions. Some leakage paths are only 0.010″ between mating surfaceswith no extra design space to fit a physical seal. Other locations arevery close to the gas path where FOD is a real concern, particularly forfragile hardware like rope, or W seals. These restrictions often lead todesigns where attempting to minimize gaps has often been a selecteddesign criteria.

SUMMARY

In one embodiment, a sealing system for a gas turbine engine includes afirst surface and a second surface spaced a dimension away from thefirst surface defining a gap through which a fluid can flow. At leastone recess is formed in one of the first surface and the second surfaceand is oriented such that the fluid flow through the gap crosses the atleast one recess. The recess is configured to restrict the fluid flowthrough the gap in comparison to if the at least one recess were notpresent, all other things being equal.

Additionally or alternatively, in this or other embodiments the at leastone recess forms sharp corners where the at least one recess intersectswith the one of the first surface or the second surface in which therecess is formed.

Additionally or alternatively, in this or other embodiments the at leastone recess is at least two recesses, a first of the two recesses beingformed in the first surface and a second of the two recesses beingformed in the second surface.

Additionally or alternatively, in this or other embodiments the first ofthe at least two recesses is positioned symmetrically across the gapfrom the second of the two recesses.

Additionally or alternatively, in this or other embodiments the first ofthe at least two recesses is positioned asymmetrically across the gapfrom the second of the two recesses.

Additionally or alternatively, in this or other embodiments the first ofthe two recesses is dimensionally identical to the second of the tworecesses.

Additionally or alternatively, in this or other embodiments the at leasttwo recesses is at least four recesses, with at least two recesseslocated at the first surface and at least two recesses located at thesecond surface.

Additionally or alternatively, in this or other embodiments thereduction in the fluid flow through the gap is restricted via rapidexpansion and contraction of the fluid flow at the at least one recess.

In another embodiment, a gas turbine engine includes a first gas turbineengine component having a first surface and a second gas turbine enginecomponent having a second surface. The second gas turbine enginecomponent positioned such that the second surface and the first surfacedefine a gap therebetween. At least one recess is formed in one of thefirst surface and the second surface and is oriented such that a fluidflow through the gap crosses the at least one recess. The recess isconfigured to restrict the fluid flow through the gap in comparison toif the at least one recess were not present, all other things beingequal.

Additionally or alternatively, in this or other embodiments the at leastone recess forms sharp corners where the at least one recess intersectswith the one of the first surface or the second surface in which therecess is formed.

Additionally or alternatively, in this or other embodiments the at leastone recess is at least two recesses, a first of the two recesses beingformed in the first surface and a second of the two recesses beingformed in the second surface.

Additionally or alternatively, in this or other embodiments the first ofthe at least two recesses is positioned symmetrically across the gapfrom the second of the two recesses.

Additionally or alternatively, in this or other embodiments the first ofthe at least two recesses is positioned asymmetrically across the gapfrom the second of the two recesses.

Additionally or alternatively, in this or other embodiments the first ofthe two recesses is dimensionally identical to the second of the tworecesses.

Additionally or alternatively, in this or other embodiments the at leasttwo recesses is at least four recesses, with at least two recesseslocated at the first surface and at least two recesses located at thesecond surface.

Additionally or alternatively, in this or other embodiments thereduction in the fluid flow through the gap is restricted via rapidexpansion and contraction of the fluid flow at the at least one recess.

In yet another embodiment, a method of sealing fluid flowing in a gasturbine engine includes abruptly enlarging and then closing a dimensionbetween a first surface of a first gas turbine engine component and asecond surface of a second gas turbine engine component along a lengthof a gap between the first surface and the second surface. A fluidflowing in the gap is expanded and contracted via the abrupt enlargementand closing of the dimension. The flow of fluid through the gap isrestricted via the expansion and contraction of the fluid along the gap.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the present disclosure isparticularly pointed out and distinctly claimed in the claims at theconclusion of the specification. The foregoing and other features, andadvantages of the present disclosure are apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIG. 1 illustrates a schematic cross-sectional view of an embodiment ofa gas turbine engine;

FIG. 2 illustrates an example of a component interface in a gas turbineengine;

FIG. 3 illustrates an embodiment of a sealing arrangement at a componentinterface of a gas turbine engine;

FIG. 4 illustrates another embodiment of a sealing arrangement at acomponent interface of a gas turbine engine;

FIG. 5 illustrates yet another embodiment of a sealing arrangement at acomponent interface of a gas turbine engine;

FIG. 6 illustrates still another embodiment of a sealing arrangement ata component interface of a gas turbine engine.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of a gas turbine engine 10. The gasturbine engine generally has a fan 12 through which ambient air ispropelled in the direction of arrow 14, a compressor 16 for pressurizingthe air received from the fan 12 and a combustor 18 wherein thecompressed air is mixed with fuel and ignited for generating combustiongases.

The gas turbine engine 10 further comprises a turbine section 20 forextracting energy from the combustion gases. Fuel is injected into thecombustor 18 of the gas turbine engine 10 for mixing with the compressedair from the compressor 16 and ignition of the resultant mixture. Thefan 12, compressor 16, combustor 18, and turbine 20 are typically allconcentric about a common central longitudinal axis of the gas turbineengine 10. In some embodiments, the turbine 20 includes one or moreturbine stators 22 and one or more turbine rotors 24.

The gas turbine engine 10 may further comprise a low pressure compressorlocated upstream of a high pressure compressor and a high pressureturbine located upstream of a low pressure turbine. For example, thecompressor 16 may be a multi-stage compressor 16 that has a low-pressurecompressor and a high-pressure compressor and the turbine 20 may be amultistage turbine 20 that has a high-pressure turbine and alow-pressure turbine. In one embodiment, the low-pressure compressor isconnected to the low-pressure turbine and the high pressure compressoris connected to the high-pressure turbine.

The gas turbine engine 10 includes mating parts with gaps therebetween,either by design and/or as a result of manufacturing tolerances.Referring to FIG. 2, gaps may exist, for example, between a firstcomponent, such as a turbine stator segment 22, and a second component,such as a turbine outer air seal 26, or between circumferentiallyadjacent stator segments 22 and outer air seals 26. While turbine statorand outer air seals are described herein, it is to be appreciated thatthe first component and second component may denote any one of manyadjacent component arrangements in the gas turbine engine 10, which mayresult in a leakage path between the first component and secondcomponent. These components may reside in the turbine 20, the compressor16, combustor 18, or other portion of the gas turbine engine 10.

Shown in FIG. 3 is a nonlimiting embodiment of a sealing arrangementbetween the stator segment 22 and the outer air seal 26. The statorsegment 22 includes stator surface 28, which is axially offset somedimension from an air seal surface 30 of the outer air seal 26, defininga gap 32 between the stator surface 28 and the air seal surface 30. Insome embodiments, the gap is about 0.010″ or less. In other embodiments,the gap 32 is greater than 0.010″.

A stator recess 34 is located along the stator surface 28 at the gap 32,and extends inwardly into the stator segment 22 to a stator recess depth36. Similarly, an air seal recess 38 is located along the air sealsurface 30 at the gap 32, opposite to the stator recess 34. The statorrecess 34 and the air seal recess 38 define an expansion chamber 40across the gap 32, such that airflow 42 flowing through the gap 32expands at the expansion chamber 40. Downstream of the expansion chamber40, the airflow is then quickly contracted again at the gap 32. Thisexpansion and contraction of the airflow 42 in quick succession induceslosses in the airflow 42 to restrict airflow 42 through the gap 32. Theairflow 42 is unable to follow the abrupt change in boundary at thestator recess 34, leading to pockets of turbulent eddys at the statorrecess 34, which dissipates mechanical energy of the airflow 42. Whenthe mechanical energy of the airflow 42 is reduced, driving force,speed, pressure, total leakage and so forth are reduced. The statorrecess 34 and the air seal recess 38 may be symmetrically locateddirectly opposite each other across the gap 32, or alternatively asshown in FIG. 4 may be asymmetrically located, e.g., staggered relativeto each other along the gap 32.

Referring again to FIG. 3, the stator recess 34 and the air seal recess38 may have equal recess widths 44 and/or equal recess depths 36, or maybe differently shaped as selected. A stator transition 46 between thestator surface 28 and the stator recess 38 is defined by a sharp corner,as is an air seal transition 48. The sharp transitions aid in achievinga quick expansion and contraction of the airflow 32. The stator recess34 and/or the air seal recess 38 may include a fillet 50 at the recessdepth 36 to reduce stresses in the stator recess 34 and/or the air sealrecess 38.

Examples of alternate embodiments of seal arrangements are illustratedin FIG. 5 and FIG. 6. In FIG. 5, the seal arrangement includes only onerecess, either the stator recess 34 or the air seal recess 38. Referringnow to FIG. 6, in another embodiment multiple pairs of stator recesses34 and air seal recesses 38 are utilized to define two or more expansionchambers 40.

The sealing arrangements described and illustrated herein do not requireadditional hardware to implement, and may be applied to new engineconfigurations and are also able to be implemented in legacy engineconfigurations as refurbishment improvements. The seal arrangementreduces the risk of foreign object damage, and is able to be implementedin small design spaces, such as on small components of the gas turbineengine or across small gaps between components where traditional sealarrangements are impractical. The sealing arrangement does not requireadherence to close tolerances and adds no loading or wear to thecomponents. The sealing arrangement can easily be customized forspecific locations and offer sealing possibilities to completely newlocations in the gas turbine engine where traditional sealingarrangements are not utilized. Analysis shows leakage reductions of 14%to 36% compared to interfaces without a sealing arrangement.

While the present disclosure has been described in detail in connectionwith only a limited number of embodiments, it should be readilyunderstood that the present disclosure is not limited to such disclosedembodiments. Rather, the present disclosure can be modified toincorporate any number of variations, alterations, substitutions orequivalent arrangements not heretofore described, but which arecommensurate with the scope of the present disclosure. Additionally,while various embodiments of the present disclosure have been described,it is to be understood that aspects of the present disclosure mayinclude only some of the described embodiments. Accordingly, the presentdisclosure is not to be seen as limited by the foregoing description,but is only limited by the scope of the appended claims.

The invention claimed is:
 1. A sealing system for a gas turbine engine,comprising: a first surface disposed at a first rotationally stationarycomponent of the gas turbine engine, the first surfaceradially-extending relative to a gas turbine engine central axis; asecond surface disposed at a second rotationally stationary component ofthe gas turbine engine, the second surface radially-extending relativeto the gas turbine engine central axis and axially offset from the firstsurface defining an axial gap through which a fluid can flow; and atleast one recess formed in one of the first surface and the secondsurface oriented such that the fluid flow through the axial gap crossesthe at least one recess, the recess configured such that the axial gapis enlarged at the recess, the recess urging expansion and thencontraction of the fluid flow through the axial gap, thereby inhibitingfluid flow through the axial gap, the at least one recess including afirst axially-extending recess surface, a second axially-extendingrecess surface offset from the first axially-extending recess surface,and a radially-extending recess surface extending from the firstaxially-extending recess surface to the second axially-extending recesssurface.
 2. The sealing system of claim 1, wherein the at least onerecess forms sharp corners where the at least one recess intersects withthe one of the first surface or the second surface in which the recessis formed.
 3. The sealing system of claim 1, wherein the at least onerecess is at least two recesses, a first of the two recesses beingformed in the first surface and a second of the two recesses beingformed in the second surface.
 4. The sealing system of claim 3, whereinthe first of the at least two recesses is positioned symmetricallyacross the gap from the second of the two recesses.
 5. The sealingsystem of claim 3, wherein the first of the at least two recesses ispositioned asymmetrically across the gap from the second of the tworecesses.
 6. The sealing system of claim 3, wherein the first of the tworecesses is dimensionally identical to the second of the two recesses.7. The sealing system of claim 3, wherein the at least two recesses isat least four recesses, with at least two recesses disposed at the firstsurface and at least two recesses disposed at the second surface.
 8. Thesealing system of claim 1, wherein the fluid flow through the gap isinhibited via rapid expansion and contraction of the fluid flow at theat least one recess.
 9. A gas turbine engine comprising: a firstrotationally stationary gas turbine engine component having a firstsurface, the first surface radially-extending relative to a gas turbineengine central axis; a second rotationally stationary gas turbine enginecomponent having a second surface radially-extending relative to the gasturbine engine central axis, the second surface axially offset from thefirst surface to define an axial gap therebetween; at least one recessformed in one of the first surface and the second surface oriented suchthat a fluid flow through the gap crosses the at least one recess, therecess configured such that the axial gap is enlarged at the recess, therecess urging expansion and then contraction of the fluid flow throughthe axial gap, thereby inhibiting fluid flow through the axial gap, theat least one recess including a first axially-extending recess surface,a second axially-extending recess surface offset from the firstaxially-extending recess surface, and a radially-extending recesssurface extending from the first axially-extending recess surface to thesecond axially-extending recess surface.
 10. The gas turbine engine ofclaim 9, wherein the at least one recess forms sharp corners where theat least one recess intersects with the one of the first surface or thesecond surface in which the recess is formed.
 11. The gas turbine engineof claim 9, wherein the at least one recess is at least two recesses, afirst of the two recesses being formed in the first surface and a secondof the two recesses being formed in the second surface.
 12. The gasturbine engine of claim 11, wherein the first of the at least tworecesses is positioned symmetrically across the gap from the second ofthe two recesses.
 13. The gas turbine engine of claim 11, wherein thefirst of the at least two recesses is positioned asymmetrically acrossthe gap from the second of the two recesses.
 14. The gas turbine engineof claim 11, wherein the first of the two recesses is dimensionallyidentical to the second of the two recesses.
 15. The gas turbine engineof claim 11, wherein the at least two recesses is at least fourrecesses, with at least two recesses disposed at the first surface andat least two recesses disposed at the second surface.
 16. The gasturbine engine of claim 9, wherein the fluid flow through the gap isinhibited via rapid expansion and contraction of the fluid flow at theat least one recess.
 17. A method of sealing fluid flowing in a gasturbine engine, comprising: abruptly enlarging and then closing adimension between a first surface of a first rotationally stationary gasturbine engine component and a second surface of a second rotationallystationary gas turbine engine component along a length of an axial gapbetween the first surface and the second surface, the first surface andthe second surface radially-extending relative to a gas turbine enginecentral axis, the first surface axially offset from the second surfacethereby defining the axial gap therebetween, the abruptly enlarging andthen closing of the dimension occurring at a recess formed in one of thefirst surface and the second surface, the recess including a firstaxially-extending recess surface, a second axially-extending recesssurface offset from the first axially-extending recess surface, and aradially-extending recess surface extending from the firstaxially-extending recess surface to the second axially-extending recesssurface; rapidly expanding and then contracting a fluid flowing in theaxial gap via the abrupt enlargement and contraction thereof; andinhibiting the flow of fluid through the axial gap via the expansion andthen contraction of the fluid along the axial gap.